CATV video and data transmission system with RF input

Abstract

Improved systems and methods for delivering CATV content over a fiber optic network from a transmitter.

The invention claimed is: 
     
       1. A method for delivering CATV content between a head end and a node over a fiber optic network, said method comprising:
 (a) receiving a radio frequency (RF) spectrum including CATV content; 
 (b) encoding the signals in the RF spectrum based on a modulation format for a destination node; 
 (c) frequency converting the encoded signals and generating a digital representation of a RF spectrum comprising a series of digital codewords, each codeword representing an instantaneous power level of the RF spectrum based on a high speed conversion clock,
 wherein said digital codewords are generated based on the high speed conversion clock without generating a corresponding RF waveform, the generated codewords represent a relative power level of the composite RF spectrum at intervals of the conversion clock, and the conversion clock is at least twice the maximum frequency contained in the RF spectrum; and 
 
 (d) propagating said digital codewords onto said fiber optic network, said digital signal representing said RF spectrum of said CATV content. 
 
     
     
       2. The method of  claim 1  where said digital signal is delivered to said fiber optic network at at least one of: 256 QAM, 1024 QAM, or 4096 QAM. 
     
     
       3. The method of  claim 1  where said digital codewords are generated in the head-end without digital to analog or analog to digital conversion of the received signals. 
     
     
       4. The method of  claim 1  where said digital signal is delivered over said fiber optic network to a said node over 1 km away from said head end. 
     
     
       5. The method of  claim 1  wherein conversion of the digital signal to analog is performed remotely at the node. 
     
     
       6. The method of  claim 1  wherein the generated codewords are input to a digital processing subsystem in order to prepare them for serial transmission for conversion by a digital to analog converter located remote to the head-end. 
     
     
       7. A transmitter in a head-end, the transmitter comprising:
 (a) an input that receives a radio frequency (RF) spectrum including CATV content; 
 (b) an encoder for encoding the signals in the RF spectrum based on a modulation format for a destination node; 
 (c) a digital up-converter for frequency converting the encoded signals and generating a digital representation of a RF spectrum comprising a series of digital codewords, each codeword representing an instantaneous power level of the RF spectrum based on a high speed conversion clock,
 wherein said digital codewords are generated based on the high speed conversion clock without generating a corresponding RF waveform, the generated codewords represent a relative power level of the composite RF spectrum at intervals of the conversion clock, and the conversion clock is at least twice the maximum frequency contained in the RF spectrum; and 
 
 (d) an emitter that propagates said digital codewords from said head end to a node through a fiber optic network. 
 
     
     
       8. The transmitter of  claim 7  where said emitter is at least one of a directly modulated laser, an externally modulated laser, an externally modulated coherent laser, and an EML transmitter. 
     
     
       9. The transmitter of  claim 7  where said emitter is externally modulated and including an Optical Duo-Binary (ODB) encoder. 
     
     
       10. The transmitter of  claim 9  including an ODB pre-coder. 
     
     
       11. The transmitter of  claim 10  including a Clock Data Recovery (CDR) retimer operatively between said ODB precoder and said ODB encoder. 
     
     
       12. The transmitter of  claim 7  including a CDR retimer. 
     
     
       13. The transmitter of  claim 7  including inband management insertion. 
     
     
       14. The transmitter of  claim 7  where said digital signal is Wavelength Division Multiplexed (WDM). 
     
     
       15. The transmitter of  claim 7  wherein said transmitter includes a Direct Digital Synthesis (DDS) module. 
     
     
       16. The transmitter of  claim 15  wherein said DDS module includes a digital up-converter (DUC) that prepares said digital signals for DAC conversion, but where said transmitter is free from including a DAC along the signal path between said input and a laser emitter of said transmitter. 
     
     
       17. The transmitter of  claim 7  wherein said digital codewords are generated based on the high speed conversion clock without generating a corresponding RF waveform. 
     
     
       18. The transmitter of  claim 7  wherein said digital signal is delivered over said fiber optic network to a said node over 1 km away from said head end. 
     
     
       19. The transmitter of  claim 7  wherein conversion of the digital signal to analog is performed remotely at the node. 
     
     
       20. The transmitter of  claim 7  wherein the generated codewords are input to a digital processing subsystem in order to prepare them for serial transmission for conversion by a digital to analog converter located remote to the head-end.